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except when oil penetrated the Santa Barbara harbor. Beaches were clcmed
toxicity. 4. A fourth factor that may be of considerable importance is the effect of
freshwater outflow. Outflow of fresh water from the estuaries is likely to be a major factor in prevention of damage in the sheltered nursery areas lying shoreward of the barrier islands. This outflow can be important in two ways:
The low salinity residual currents flowing out of the interisland passes will tend to hold any oil slicks offshore except perhaps under conditions of strong onshore winds that might create a surface current
that would override the current caused by freshwater outflow.
adsorption (or sorption) of oil on the suspended detrital particles
Barbara oil spill, as shown in the following figure from his report. The northern Gulf estuaries are relatively shallow, muddy, nutrient rich areas, borded by extensive areas of salt marsh. They provide nursery area for practically every commercially valuable species sought after in the northern Gulf. The high particulate content of the estuarine waters may
precipitate out many of the detrimental components of the oil. An oil spill may affect the immediate local area and in some cases cause biologic changes which may persist for several years, but it docs not cause permanent biolo:ic damage. The repopulation of marine organisms in the affected area begins within one or two biologic cycles. This is documented by past spills.
A spill of more than 3,000 barrels of #2 fuel oil a finished petroleum product at West Falmouth, Massachusetts, in 1969 is known to have killed large numbers of marine organisms in the sublittoral zone, and the shellfish were helieved unsuitable for harvesting or sale for many months, An independent study two years later observed a healthy biologic community present in the area.
The wreck of the Tampico Maru in 1957 spilling #2 fuel oil a finished petroleum product on the Baja, California coast caused heavy and immediate mortality to much of the fauna in the area. Although substantial recovery of marine life occurred within a year, sone effects of the spill were evident several years later.
The widely publicized Santa Barbara crude oil spill of January, 1969, caused the death of sca birds and temporarily coated large stretches of adjacent beach. However later studies of the effect on marine life in the area revealed no permanent damage.
The crude oil spill from the Torrey Canyon likewise resulted in little or no persistent damage to marine organisms in England or France.
The severity of the biologic effects of a spill depends upon many variables. The degree of the immediate biologic effect is greater with some petroleum products than with crude oil. Other factors are also important. The amount of spilled oil, of course, is one of them. A lot of oil in a small area naturally is going to have more effect than the same amount of oil over a larger area. The physiography of the area will be important in determining the length of time the oil stays in the area and how widely it is dispersed. Season, weather conditions at the same time of the spill, other environmental stresses and the way the oil is cleaned up will all have some bearing on the degree of contact of the oil with marine organisms.
Environmental Comparison of Deepwater Port Sites East and West of the Mississippi River Delta
Under normal circumstances, the superport located anywhere along the 20-fathom contour in the east north central Gulf of Mexico would have no appreciable detrimental effect on the environment. However, such a port located off the coast to the west of the Mississippi River Delta, although considered environmentally safe under such normal circunstances, in the event of some unforeseen disaster which may result in oil spillage, appears to be significantly less desirable than a location to the east of the Delta. The factors responsible for these differences are discussed below.
Freshwater input. A large amount of freshwater leaves the coastal plain via river systems between Mobile Bay and the Mississippi River (sce Appendix tables). This water flows into the Gulf at the surface through passes between the barrier islands. Thus there is a net offshore surface movement of water, which would retard or prevent oil reaching the estuaries in the event of an offshore spill. There is comparatively little freshwater runoff west of the Delta, and its movement offshore is diffuse and thus less effective in resisting potential onshore movement of an oil film. Currents. Current data indicates that the mass movement of water east of the Mississippi River Delta appears to be eastward and slightly to the south, thus a new movement away from shore. This is in part related to freshwater movements cited above. The dominant water movement west of the Delta is westward toward the Louisiana and Texas estuaries. Barrier islands. The coastline between Mobile Bay and the Mississippi River is guarded by barrier islands (see Figure 2), which form a physical obstruction against the movement of oil into estuaries and onto the mainland. Such islands are absent from the Mississippi River westward to Galveston. Thus the estuaries of the Louisiana coastline are directly exposed to an onshore movement of oil. Wind shelter. Depending on speed and direction, the biggest single factor influencing movement of an oil spill may be wind. In considering sites cast of the Delta it should be noted that the fetch of southwest winds is obstructed by the Delta, whereas the southwest wind blows directly onshore during a large portion of the year along the northern Gulf west of the Delta. This could be an important consideration in the safe berthing of large vessels, and have a bearing on the inshore movement of oil slicks. Sediment influence on spills. The large amount of sediment-laden freshwater flowing se award out of the passes between the barrier islands east of the Delta should afford more protection to the estuaries against oil spills (see Figure 3), than is the case west of the Delta where the estuaries do not discharge as great a volume of freshwater.
In the interest of preserving the ecology of the offshore islands and coastal zone with regard to possible oil spills or other incidents considered harmful to the environment, location of the superport is recommended south of 29° 50'. This restriction on the location would allow sufficient time to execute an expedient oilcleanup in the event of a spill. Locating the port at this latitude and at approximately longitude 88° 15'W (no further west) will place the port in the most favorable position to take advantage of the high density water mass that travels in a cyclonic manner around the lighter water over the shelf due to the Mississippi River discharge. This entrainment by the prevailing current regime would tend to kcep the spilled oil offshore for a period of time, provided there were no adverse winds, allowing cleanup operations to be undertaken.
Winter would be the safest period in the event of a spill with the combination of favorable factors being the high rates of river discharge and offshore winds. The most unfavorable period would be during the summer and fall with low rates of river discharge and southerly winds.
REFERENCES AND DATA SOURCES
Brahtz, J. S. (Ed). 1968.
Ocean Engineering, John Wiley and Sons, New York.
Christmas, J. J. Data and figures from a forthcoming report on Mississippi estuaries.
Gulf Coast Research Laboratory, Ocean Springs, Mississippi. Cochrane, J. D. 1963. "Yucatan Current," in Unpublished report of the Department of
Oceanography and Meteorology, A & M College of Texas. Reference 63-18A. Cronin, Eugene (Coordinator), E. W. Fager, M. G. Gross, G. Gunter, D. Hood, D. W.
Pritchard, and E. Salo. 1971. Preliminary analysis of the ecological aspects : of deep port creation and superships operation. Department of the Army, Corps of Engineers, Institute for Water Resources, Report 71-10:31p.
Curray, J. R. 1960. Sediments and history of Holocene transgression, continental
shelf, northwest Gulf of Mexico, In Recent Sediments, Northwest Gulf of Mexico;
Franks, J. S., J. Y. Christinas, W. L. Siler, Combs, R. Waller and C. Burns. 1972.
study of nektonic and benthic faunas of the shallow Gulf of Mexico off the State of Mississippi. Gulf Research Reports 4(1):1-148.
Groen, T. 1967. The waters of the Sea, D. Van Nostrand. London.
Kolpack, Ronald L. 1971. Biological and oceanographical survey of the Santa Barbara
oil spill, 1969-1970. Vol. II, Physical, chemical and şcological studies.
Moore, D., H. A. Brusher and L. Trent. 1970. Relative abundance, seasonal distribu
tion, and species composition of demersal fishes off Louisiana and Texas.
National Marine Fisheries Service.
Data from D. J. Bond, Bayou La Batre statistical agent on shrimp landings by
tal fishing results in the area from 1950 through 1972. Nicholson, Nancy L., and Robert L. Cimberg. 1971. The Santa Barbara oil spills of
1969: A post-spill survey of the rocky intertidal. Chap. 17:325-400. In Biological and oceanoyraphical survey of the Santa Barbara channel oil spill, 1969-1970. Vol. I, Biology and Bacteriology, Allan Hancock Foundation, University
of Southern California. Roithmayr, c. M. 1965. Industrial bottom fish fishery of the northern Culf of Mexico,
1959-63. U. S. Fish and Wildlife Service Spec. Sci. Rept. - Fisheries No. 518, 23 p.